This adds a dark mode toggle to both user interface views (compact and tabbed view).
In addition, this code fixes the problem that the initial theme did not load properly
based on settings. Equally, the Toggle in Notebookbar will now appear
"selected" when pressed.
Signed-off-by: ChrisGlad <chris.gladman2004@gmail.com>
Change-Id: I0e0c282cec24d9bb7fbfc4131ba3875976cea5fd